User`s guide

46 DC 900-1516D
ICP2432 User’s Guide for OpenVMS Alpha (DLITE Interface)
returned. Returning the cancelled request reduces the number of I/O completions
by one.
• Because cancelled I/O is considered completed, cancelled requests are also
returned in response to requests for completed reads and writes (using
dlPoll).
These requests are returned with the
DLI_IO_ERR_IO_CANCELLED error code.
• This implementation of cancel processing supports those applications designed
for the Freeway DLI.
• The user application should ignore the buffer length and associated buffer data
when a cancelled I/O request is returned.
dlRead
There is no change to the dlRead function. However, because DLITE supports Raw
operation only, it does require an associated
OptArgs with each I/O request. DLITE fills
in the supplied
OptArgs structure with the appropriate data from the ICP and Protocol
headers associated with the read data received from the ICP. Read requests (
dlRead) are
returned to the application with the supplied
OptArgs structure built from the ICP and
Protocol header received with the data buffer. All the ICP and protocol information is
available in the
OptArgs structure when the read buffer is returned.
Non-blocking I/O should expect an
EWOULDBLOCK error upon return. A callback is
issued when the read is completed. A callback is invoked for each (both read and write)
read completion.
If the read operation is returned with an error, the data in the
OptArgs structure is not
valid. The application must verify the read operation before referencing
OptArgs data.